A clinical trial of an experimental vaccine against the deadly Ebola virus, which has killed nearly 1,000 people in West Africa, is expected to begin soon.

British drug maker GlaxoSmithKline (GSK) is co-developing the vaccine with US scientists which is said to have produced promising results in animal studies involving primates.

The drug is to enter Phase I testing in humans pending approval from US Food and Drug Administration.

There is no proven cure or vaccine to prevent Ebola and the scale of the current outbreak has prompted the World Health Organisation (WHO) to declare it an international health emergency.

A GSK spokeswoman said the trial should get underway "later this year", while GSK's partner the US National Institute of Allergy and Infectious Diseases (NIAID) said in a statement it would start "as early as fall 2014", implying a potential September launch of testing.

Even if is fast-tracked, and emergency procedures are put in place, the new vaccine could not be ready for widespread deployment before 2015 assuming the drug works.

"It is right at the beginning of the development journey and still has a very long way to go," the GSK official said.

NIAID - part of the National Institutes of Health - is also supporting work on other early-stage Ebola vaccines, including one from Johnson & Johnson's Crucell unit that should enter Phase I clinical testing in late 2015 or early 2016.

Aid workers put into quarantine in the US

Missionaries and other people returning to North Carolina from Africa after working with people with Ebola are being placed in quarantine as a precaution against the spread of the disease.

The quarantine period is set to last for three weeks from the last exposure to someone infected in the West African Ebola outbreak, which is centered in Guinea, Sierra Leone and Liberia, officials said.

Missionaries from the North Carolina-based Christian aid groups SIM USA and Samaritan's Purse have been working to help combat the world's worst outbreak of the disease.

Two of the relief workers contracted the disease and are being cared for at Emory University in Georgia.

"This measure is being taken out of an abundance of caution, and it is important to remember that there are no confirmed or suspected cases of Ebola in North Carolina," Dr Stephen Keener, medical director in North Carolina's Mecklenburg County, said in a statement.

SIM USA said yesterday some of its missionary staff based in Liberia will be returning to Charlotte.

UN expects number of Ebola cases to climb

UN World Health Organisation assistant director-general for health security, Keiji Fukuda, said on Sunday there have been 1,825 cases reported, with the mortality rate running about 55 to 60 per cent.

He said he expects the number of infections to increase.

"What is difficult in this situation is that we are dealing with countries with weak health systems. And we are dealing with areas in which practices like good infection prevention and control practices are not the norm in some of the hospitals and in families and communities," Dr Fukuda said.

Liberians have packed churches in the capital Monrovia on Sunday to defy official warning about public gatherings to pray.

Martee Jones Seator at Saint Peter's Lutheran Church said people are afraid.

"Ebola is not going to shake our faith in anyway ... because we've been through difficult times."

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